This invention generally relates to passive radar decoys and more particularly to a self-inflated aero-dynamic body incorporating a unique RF retro-reflective configuration for radar target enhancement and improved radar cross section at millimeter frequencies.
The use of chaff to defeat the radar function by denying it range and direction (azimuth and elevation) information is a well known and practiced technique in the art of radar jamming and/or countermeasures. Passive chaff elements in the form of discrete dipoles are dispensed by an aircraft to form a distince cloud which creates a credible false target to the ground-based radar. The dipoles are generally low mass slivers of metalized milar, glass, or other suitable dialectric material and these are very compactly and densely packaged into canisters and loaded into ejection equipment aboard the aircraft. The ejection equipment fire the chaff out of the canisters and into the aircraft windstream where vehicle-induced turbulance or wind shear effects are available for cloud dispersion. The low mass chaff slivers, upon being ejected, rapidly slow down and fall at an almost constant rate. For example, a widely used one mil metalized glass chaff has a settling rate of about 50 feet per minute.
One of the problems with present chaff systems is that the low mass slivers are easily damaged by the high compressive force necessary to eject them from the canister and into the aircraft windstream. Being compressed, the chaff dipoles may not uniformly disperse in the windstream and will therefore not provide the desired radar countermeasures performance.
Another problem with present chaff systems is the fact that the low mass slivers rapidly slow down upon ejection and therefore the useful life is shortened for lack of a doppler frequency return to the radar. Thus, the radar can update its return information and easily determine the location of the aircraft because of its doppler frequency.
It is in accordance with one aspect of the present invention, an object to provide a highly effective false target for enhancement of radar target cross section.
It is in accordance with another aspect of the invention, an object to provide a self-inflated, passive radar decoy that achieves coverage at millimeter wave frequencies and upon ejection from an aircraft provides a scintillating and doppler frequency return to a ground-based radar.
In accordance with still another aspect of the invention, it is an object to provide a ram-air inflated passive decoy that has a unique RF retro-reflective configuration for millimeter wave radar target performance.
The various aspects and advantages of the invention are met in a passive radar decoy comprising a substantially hemispherical upper body portion having an inner surface coated with an RF reflective material, a weighted nose piece, a tapered lower body portion interconnecting the upper body to the nose piece, an RF reflectively-coated corner reflector mounted coaxially within the hemispherically-shaped upper body portion; and means to ram-air inflate the decoy when it is released from the aircraft such that RF energy from a ground source of such energy impinges on the RF reflective surfaces to retro-reflectively return said RF energy back to the source of said energy and provide a scintillating and doppler frequency return and enhanced radar target cross section.